Marine Weather Net

Straits of Florida from west end of Seven Mile Bridge to south of Halfmoon Shoal out 20 to 60 NM Marine Forecast


THIS AFTERNOON

NE
WINDS
20 - 25
KNOTS

TONIGHT

ENE
WINDS
20 - 25
KNOTS

THURSDAY

THURSDAY NIGHT

E
WINDS
15 - 20
KNOTS

The Marine Weather Forecast In Detail:
GMZ074 Forecast Issued: 1027 AM EST Wed Dec 02 2020

SMALL CRAFT ADVISORY IN EFFECT
This Afternoon...Northeast Winds 20 To 25 Knots. Seas 5 To 8 Feet.
Tonight...Northeast To East Winds 20 To 25 Knots. Seas 6 To 9 Feet.
Thursday...East Winds Decreasing To 15 To 20 Knots. Seas 5 To 8 Feet, Subsiding To 4 To 7 Feet.
Thursday Night...East Winds 15 To 20 Knots. Seas 4 To 6 Feet. Isolated Showers.
Friday...East To Southeast Winds 10 To 15 Knots. Seas 3 To 5 Feet. Isolated Showers.
Friday Night...Southeast To South Winds 10 To 15 Knots. Seas 2 To 3 Feet. Scattered Showers.
Saturday...Southwest Winds Near 10 Knots, Becoming West To Northwest In The Afternoon. Seas 1 To 2 Feet. Scattered Showers.
Saturday Night...Northwest To North Winds 10 To 15 Knots. Seas 2 To 4 Feet, Building To 3 To 6 Feet. Isolated Showers.
Sunday...North Winds 10 To 15 Knots. Seas 3 To 6 Feet. Isolated Showers.
Sunday Night...Northwest To North Winds 10 To 15 Knots. Seas 2 To 4 Feet.
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Synopsis for Keys coastal waters from Ocean Reef to Dry Tortugas: GMZ005
1027 AM EST Wed Dec 2 2020

Fresh to strong northeast to east breezes will prevail today and tonight across most of the Keys coastal waters. East breezes will slowly but gradually diminish Thursday into Friday before the next cold front approaches the Keys this weekend, likely blasting through the coastal waters Saturday or Saturday night.

Gulf Stream
The Approximate Shoreward Edge of the Gulf Stream as of December 1...
- 45 NM South of Dry Tortugas Light...on Loggerhead Key.
- 49 NM South of Cosgrove Shoal Light...off the Marquesas Keys.
- 40 NM South of Sand Key Light...off Key West.
- 1 NM South of Looe Key...off Big Pine Key.
- 2 NM South of Sombrero Key Light...off Marathon.
- 1 NM Southeast of Alligator Reef Light...off Islamorada.
- 1 NM Southeast of Molasses Reef Light...off Key Largo.
- 2 NM East of Carysfort Reef Light...off Ocean Reef.
Area Forecast Discussion
...CORRECTED National Weather Service Key West FL
1059am EST Wednesday Dec 2 2020

A pretty and serene, albeit breezy, morning across the Florida Keys. Skies across the island chain are cloudless. Any and all clouds are over the Florida Straits and western Atlantic waters. Visible satellite and radar shows a sharp and narrow area of convergence occurring as a surface high pressure centered over the middle Tennessee Valley is trekking northeast. As it moves, winds are trying to veer around to the northeast and east northeast. This can be seen based on observations over the Bahamas and Cuba. However, closer to home winds coming off the southern mainland and moving over relatively cooler waters when compared to the warm Florida Straits. Therefore winds have a tendency to back and stay more north of northeast. This subtle wind shift is enough to cause some convergence east and south of the Florida Keys. Meanwhile, another interesting weather phenomenon is occurring as gentle isentropic upglide is occurring in the 700 mb level south and southwest of the Lower Keys. This is causing some addition convergence and clouds to develop. This is evident looking at analysis as well as satellite signatures. Clouds caused by the upglide are moving northwest initially before being pushed by the dominant flow which is from the east northeast to northeast.

Geeky weather talk aside, breezy conditions persist across the Keys with surface observations showing 15 to 20 mph with occasional gusts to 25 mph. Meanwhile over our coastal waters, speeds range from 17 knots to 21 knots, highest across our western C-MAN stations. Temperatures remain a cool and crisp 67 degrees at the Key West Airport, with dew points in the mid to upper 50s.

Short Term Update
No changes were made to the zone forecasts and only minor changes made to the coastal waters forecast. Cooler waters over Florida Bay, along with a developing thermal trough over the mainland is leading to a slackening of winds over Florida Bay. As such, have dropped the Small Craft Advisory for these waters, while maintaining SCA (Small Craft Advisory) across the remaining waters. Dry and pleasant weather will prevail through the end of the week. The previously mentioned high pressure will continue to trek northeast, reaching the Carolinas by Thursday and then offshore Friday. This will lead to winds gradually clocking around towards the east and allow for low level moisture to increase. An approaching upper level trough from our west will provide additional moisture in the mid and upper levels starting Friday and continuing into Sunday. All of this will lead to an increase in rain chances ahead of the next approaching front possibly late Sunday.

Marine
Small Craft Advisories remain in effect for all waters except Florida Bay. Across the waters, a Small Craft Exercise Caution headline is in effect. Fresh to occasionally strong breezes will persist across most of the Florida Keys coastal waters through tonight and at least Thursday morning. Thereafter, winds gradually slacken through Saturday. Timing remains uncertain with the next front though it could pass through the area Sunday. A stronger reinforcing front arrives late Monday or early Tuesday with freshening breezes.

NOAA Key West FL Office: Watches - Warnings - Advisories
FL...None. GM...Small Craft Advisory for GMZ032>035-042>044-052>055-072>075.